Field of the Invention
The invention relates to the field of track etching methodologies for forming nanopores in inorganic membranes.
Description of the Prior Art
Membranes containing straight pores are often prepared by the track-etching technique. One of the most frequently used track-etch membranes are polymer films e.g. polycarbonate, polyimide, and polyesters. These films are typically several micrometers thick, which limits the flow rate when the membranes are used in filtration. The polymer material of the membranes is the reason why it is very difficult to integrate such membranes with other microfluidic or nanofluidic devices and lab-on-chip systems. The pore size of such polymer membranes cannot be controlled with sub-nanometer precision.
US Patent Publication 2006/0278580 A1 describes the making of thin silicon membranes but not other types of inorganic materials, the use of local instability of the material at high temperatures without the ability to control the porosity of the membrane (number of pores) which is crucial for many applications, especially filtration/separation, and without the ability to make pores with different shapes, e.g. conical and double-conical or to easily control of membrane thickness independently of porosity and pore size. Latent track etching techniques are well known in thin membranes, but such polymer membranes are not ultrathin and are characterized by limited flux rates.